This invention relates broadly to electrically insulated bearings and a method for manufacturing the insulated bearings. More particularly, the invention relates to methods for manufacturing insulated sleeve bearings utilized in large rotating electrical machinery.
Sleeve bearings are typically utilized to secure the shafts of large rotating electrical machines and generators. The prior art sleeve bearings generally have a machined inner surface covered with a material to provide a wear surface for the rotating shaft. The outer surface of the bearing is also usually machined. A tube of insulating material having a machined inner surface is then placed about the bearing sleeve with its inner machined surface cemented to the machined exterior surface of the sleeve.
The prior art also includes sleeve bearings having an insulating layer which is applied by spraying an alumina oxide plasma coating onto the exterior surface of the sleeve. Such procedures are complex and require precise controls to insure uniformity in the deposited layer. In addition, such coatings cannot be effectively applied to an as-cast bearing surface.
The requirement in the prior art insulated sleeve bearings that the exterior surface of the metal sleeve be machined is both time-consuming and costly. The present invention eliminates the disadvantages of the prior art insulated sleeve bearings in that it is a sleeve bearing having a metal sleeve member with an as-cast or non-machined outer surface to which is applied an electrically insulating layer. In addition to eliminating the step of machining the exterior surface of the bearing sleeve, there is also no requirement that the mating surface of the insulating layer be precisely machined to fit the bearing sleeve.